Semiconductor device for attaching to a flexible display and a method of manufacturing the same

ABSTRACT

A semiconductor device for attaching to a flexible display is provided. The semiconductor device includes a substrate including semiconductive material, and a conductive pad disposed on the substrate. Each corner of the conductive pad is free of right angle. The flexible display includes a flexible substrate including a circuit, and the semiconductor device. A method of manufacturing a flexible display includes providing a substrate including semiconductive material, and forming a conductive pad on the substrate, wherein each corner of the conductive pad is free of right angle. The method further includes providing a flexible substrate, and bonding the conductive pad to a conductor of a circuit of the flexible substrate.

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims priority of U.S. provisional application Ser.No. 62/738,423 filed on 28 Sep. 2018, which is incorporated by referencein its entirety.

BACKGROUND

A flexible display provides increased convenience due to portability andincreased screen size, and can be applied to mobile devices, such ascellular phones, portable multimedia players (PMPs), navigation devices,ultra mobile personal computers (UMPCs), e-books and e-newspapers, andalso to other fields, such as TVs, monitors, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It shouldbe noted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a top schematic view of a semiconductor device in accordancewith some embodiments of the present disclosure.

FIG. 2 is a cross-sectional view of a semiconductor device in accordancewith some embodiments of the present disclosure.

FIG. 3 is a cross-sectional view of a semiconductor device in accordancewith some embodiments of the present disclosure.

FIG. 4 is a top view of a flexible display in accordance with someembodiments of the present disclosure.

FIG. 5 is a perspective view of a flexible display in accordance withsome embodiments of the present disclosure.

FIG. 6 shows schematic views of a flexible substrate in accordance withsome embodiments of the present disclosure.

FIG. 7 is a flowchart representing a method of manufacturing a flexibledisplay according to aspects of the present disclosure in one or moreembodiments.

FIGS. 8 to 15 are cross-sectional views of a flexible display at variousstages of manufacture in accordance with some embodiments of the presentdisclosure.

FIGS. 16 and 17 are top schematic views of a flexible display at variousstages of manufacture in accordance with some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of elements and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper,” “on” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

As used herein, terms such as “first,” “second” and “third” describevarious elements, components, regions, layers and/or sections, but theseelements, components, regions, layers and/or sections should not belimited by these terms. These terms may be only used to distinguish oneelement, component, region, layer or section from another. The termssuch as “first,” “second” and “third” when used herein do not imply asequence or order unless clearly indicated by the context.

As used herein, the terms “approximately,” “substantially,”“substantial” and “about” are used to describe and account for smallvariations. When used in conjunction with an event or circumstance, theterms can refer to instances in which the event or circumstance occursprecisely as well as instances in which the event or circumstance occursto a close approximation.

In a manufacturing process of a flexible display device, a semiconductordevice, such as a driver IC, may be physically bonded or attached to theflexible display. The flexible display may be a flexible display panel(e.g., an organic light-emitting diode (OLED) panel), a flexible printedcircuit board (FPCB), or a plastic transparent liquid-crystal display(LCD) panel.

However, when bonding the semiconductor device to the flexible display,cracks or other mechanical defects such as debonding of existing layersin the semiconductor device may occur. Over time, even small cracksalong the edge of the conductive pad of the semiconductor device canpropagate towards deeper regions of the device. Cracks and other defectsgenerated in this way that encroach into a deeper region can allowmoisture to permeate into the semiconductor device, which reduces thereliability of the semiconductor device.

Integrated circuit (IC) devices are usually fabricated on semiconductorwafers having a plurality of IC device dies. Each IC includes conductivepads on its top surface that connect to various nodes in the device,such as for signal input, signal output and power supply nodes. Theconductive pads of an IC are generally connected by a wire of a leadframe or other electrically conductive structure such as a contact padon a support in order for a printed circuit board (PCB) to permitutilization of the IC die. Known methods for connecting an IC device toa lead frame or other support elements include wire bonding, tapeautomated bonding (TAB), controlled collapse chip connection (C4) orbump bonding, and electrically conductive adhesives.

Conventionally, a conductive pad disposed on a substrate includes fourright angle from the top view perspective. That is, the shape of theconductive pad is square or rectangular from the top view perspective.When the semiconductor device is being bonded to the flexible display byapplying a predetermined pressure, the semiconductor device may easilycrack, especially the region around the conductive pad. The reason forthis phenomenon is that the region around the right angle of the squareor rectangular conductive pad is the area being subjected to the moststress.

The present disclosure therefore provides a semiconductor device forattaching to a flexible display, a flexible display, and a method ofmanufacturing a flexible display. The semiconductor device for attachingto a flexible display includes a substrate including semiconductivematerial, and a conductive pad disposed on the substrate. Each corner ofthe conductive pad is free of right angle.

FIG. 1 is a top schematic view illustrating a semiconductor device forattaching to a flexible display according to aspects of the presentdisclosure in some embodiments. Referring to FIG. 1, a semiconductordevice 100 for attaching to a flexible display includes a substrate 11including semiconductive material, and a conductive pad 12 disposed onthe substrate. Each corner of the conductive pad 12 is free of rightangle. In some embodiments, the semiconductor device 100 is a driver ICfor a display. In some embodiments, the semiconductor device 100includes a plurality of conductive pads 12. The number of the conductivepads 12 has no particular limits, and the conductive pads 12 can bearranged depending on the geometrical design and dimensions of thesemiconductor device 100.

In order to avoid right angle from a top view perspective of thesemiconductor device 100, in some embodiments, the conductive pad 12 isarc-shaped from a top view perspective. The geometrical design anddimensions of the conductive pad 12 have no particular limits, and canbe, but need not necessarily be, round, oval, rectangular, square,triangle, quadrilateral, parallelogram, diamond, trapezoidal,pentagonal, hexagon, or other desired shape, as long as each corner ofthe conductive pad 12 is free of right angle, or is a rounded corner. Insome embodiments, the shape of each conductive pad 12 may be the same ordifferent. In some embodiments, the conductive pads 12 have similarfeatures. While the conductive pads 12 are described as having similarfeatures, such description is intended to be illustrative and is notintended to limit the embodiments, as the conductive pads 12 may havesimilar structures or different structures in order to meet the desiredfunctional requirements. In some embodiments, the shape of theconductive pad 12 is a parallelogram or trapezoid from a top viewperspective.

In some embodiments, the substrate 11 includes a low pad density area111. In some embodiments, when the semiconductor device is being bondedto the flexible display or any other device by applying a predeterminedpressure, the predetermined pressure can be applied to the low paddensity area 111. In some embodiments, the low pad density area 111 islocated at the center of the substrate 11. In some embodiments, the lowpad density area 111 has no conductive pad 12.

In some embodiments, the substrate 11 further includes at least two highpad density areas 112, the conductive pad 12 density of each high paddensity area 112 is higher than the conductive pad 12 density of the lowpad density area 111. In some embodiments, the low pad density area 111is located between the high pad density areas 112. In some embodiments,as shown in FIG. 1, the shape of the substrate 11 is rectangular, thelow pad density area 111 is located at the center of the substrate 11,and two high pad density areas 112 are located at both ends of the longside 113 of the rectangular substrate 11.

In some embodiments, the shape of the conductive pad 12 is aparallelogram from a top view perspective and the conductive pad 12 isslanted away from the low pad density area 111. In some embodiments, theshape of the conductive pad 12 is a parallelogram from a top viewperspective and the conductive pad 12 is slanted toward the low paddensity area 111. In some embodiments, the shape of the conductive pad12 is a parallelogram, and the parallelogram conductive pad 12 has apair of long sides and a pair of short sides from a top viewperspective. In some embodiments, the long sides of the parallelogramconductive pad 12 are sloped away from the low pad density area 111 andtoward the long side 113 of the substrate 11. In some embodiments, thelong sides of the parallelogram conductive pad 12 are sloped toward thelow pad density area 111 and toward the long side 113 of the substrate11. In some embodiments, the short sides of the parallelogram conductivepad 12 are parallel to the long side 113 of the substrate 11. In someembodiments, the short sides of the parallelogram conductive pad 12 aresloped away from the low pad density area 111 and toward the long side113 of the substrate 11. In some embodiments, the short sides of theparallelogram conductive pad 12 are sloped toward the low pad densityarea 111 and toward the long side 113 of the substrate 11. In someembodiments, the long sides of the parallelogram conductive pad 12 areparallel to the long side 113 of the substrate 11. In some embodiments,the conductive pads 12 are arranged in similar configurations. In someembodiments, the conductive pads 12 are arranged in differentconfigurations.

FIG. 2 is a cross-sectional view of the semiconductor device forattaching to a flexible display according to aspects of the presentdisclosure in some embodiments. Referring to FIG. 2, in someembodiments, the semiconductive material included in the substrate 11 isselected from the group consisting of silicon, silicon-germanium, andother semiconductor materials including III-V or II-VI materials. Insome embodiments, the substrate 11 includes at least one integratedcircuit (IC) device formed thereon. In some embodiments, semiconductordevice 100 includes a plurality of conductive features 120, wherein eachconductive feature 120 includes a conductive pad 12.

In some embodiments, the substrate 11 further includes a passivationlayer 13 surrounding the conductive pad 12. In some embodiments, thepassivation layer 13 is disposed over the conductive features 120, andthe passivation layer 13 is configured to provide a trench above eachconductive feature 120 that defines the exposed portion of eachconductive feature 120. In other words, the conductive pad 12 is theexposed portion of the corresponding conductive feature 120. In someembodiments, the conductive feature 120 includes copper, aluminum, oralloys thereof, a non-solderable pad material such as Ti metal, or a Ticompound material such as TiN, TiW, or TiAl3. In order to provide areliable and low electrical resistance attachment surface of theconductive pad 12, in some embodiments, the conductive pad 12 is amulti-layered conductive pad having a top metal layer that is bothelectrically conductive and resistant to oxidation, in order to providehigh reliability (good corrosion performance) and high performance (lowresistance).

In some embodiments, the passivation layer 13 includes dielectricmaterials such as polyimide (PI), benzocyclobutene (BCB),polybenzoxazole (PBO), silicon nitride (SiN), silicon carbide (SiC),silicon oxide (SiO), silicon oxynitride (SiON), low-k dielectrics suchas carbon doped oxides, extremely low-k dielectrics such as porouscarbon doped silicon dioxide, or combinations thereof.

In some embodiments, the conductive pad 12 is an aluminum conductivepad. Solder bumping on aluminum is known to generally not be possibledue to aluminum oxide formation during the soldering process, whichprevents solder adhesion. In some embodiments, the conductive pad 12 isan aluminum conductive pad and includes a complex stack formed on thealuminum. In some embodiments, the complex stack includes arefractory-metal based barrier layer formed on the conductive pad, acopper seed formed on the barrier layer, an electroplated copperredirect layer (RDL), and an under bump metallization (UBM) formed onthe RDL, wherein a solder bump (or ball) is formed on the UBM.

In some embodiments, the substrate 11 further includes a base layer 15,and an interlayer dielectric (ILD) layer 14 formed on the base layer 15.In some embodiments, the ILD layer 14 may include silicon oxide (SiO),silicon nitride (SiN), silicon oxynitride (SiON), silicon carbide (SiC),a low-dielectric constant dielectric material, or combinations thereof.

FIG. 3 is a cross-sectional view of the semiconductor device forattaching to a flexible display according to aspects of the presentdisclosure in some embodiments. In some embodiments, the substrate 11includes a plurality of ILD sublayers 141 formed on the base layer 15,and includes a plurality of metal interconnects 121 and 122. As shown inFIG. 3, the metal interconnects 121 and 122 are damascened into ILDsublayers 141. In some embodiments, a pre-metal dielectric (PMD) layer16 is formed between the base layer 15 and the ILD layer 14. In someembodiments, the PMD layer 16 includes thermally grown silicon oxide. Insome embodiments, the substrate 11 includes plugs 123 configured tocouple metal interconnects 122 to one node 124 a shown as a diffusion(e.g., n⁺ or p⁺) and to another node 124 b shown as a gate electrodenode (circuitry not shown), with 124 b being a contact to a metal oxidesemiconductor (MOS) gate 125 on a gate dielectric 126 on thesemiconductor surface of the base layer 15. In some embodiments, theplugs 123 include tungsten, or other suitable electrically conductiveplug material.

FIG. 4 is a top view illustrating a flexible display according toaspects of the present disclosure in some embodiments. FIG. 5 is aperspective view illustrating a flexible display according to aspects ofthe present disclosure in some embodiments. Referring to FIGS. 4 and 5,the flexible display includes a flexible substrate 21 including acircuit 22, and a semiconductor device 100 attached to the flexiblesubstrate 21. The semiconductor device 100 includes a conductive pad 12bonding to a conductor 23 of the circuit 22, and each corner of theconductive pad 12 is free of right angle. FIG. 4 shows a state in whichthe flexible substrate 21 is substantially flat, and FIG. 5 shows astate in which the flexible substrate 21 is bent. In some embodiments,the flexible display has a top emission configuration. Any suitabledisplay arrangement may be used, if desired. In some embodiments, theflexible display may be incorporated in an electronic device.

In some embodiments, the semiconductor device 100 includes a pluralityof conductive pads 12. In some embodiments, each conductive pad 12 isconfigured to output a signal to the circuit 22. In some embodiments,the circuit 22 is formed along the edge of the flexible display and iscoupled to the semiconductor device 100. In some embodiments, eachconductive pad 12 is bonded to a corresponding conductor 23 of thecircuit 22.

In some embodiments, the flexible display includes at least one displayarea (i.e., active area) 212, in which an organic light-emitting diode(OLED) is formed. One or more non-display areas (i.e., inactive area)211 may be provided at the periphery of the display area 212. That is,the non-display area 211 may be adjacent to one or more sides of thedisplay area 212. In FIG. 4, the non-display area 211 surrounds arectangular shape display area 212. However, it should be appreciatedthat the shapes of the display area 212 and the arrangement of thenon-display area 211 adjacent to the display area 212 are notparticularly limited to those shown in the exemplary flexible displayillustrated in FIG. 4. The display area 212 and the non-display area 211may be of any shape suitable to the design of the electronic deviceemploying the flexible display. Non-limiting examples of the displayarea 212 shapes in the flexible display include a pentagonal shape, ahexagonal shape, a circular shape, an oval shape, and more.

In some embodiments, the semiconductor device 100 is attached to anon-display area 211 of the flexible substrate 21. In some embodiments,the OLED is electrically connected to a gate line and a data line tocommunicate with the circuit 22, which is positioned in the non-displayarea 211 of the flexible display 100.

In some embodiments, the flexible substrate 21 may be made of a thinplastic film. In some embodiments, the flexible substrate 21 includespolyimide (PI), polyethylene naphthalate (PEN), polyethyleneterephthalate (PET), other suitable polymers, or a combination thereof.Other suitable materials that may be used to form the flexible substrate21 include a thin glass, a metal foil covered with a dielectricmaterial, a multi-layered polymer stack and a polymer composite filmcomprising a polymer material combined with nanoparticles ormicro-particles dispersed therein, and combinations thereof.

In some embodiments, bending the non-display area 211 results inminimization or elimination of a view of the non-display area 211 fromthe front side 41 of the assembled flexible display. A part of thenon-display area 211 that remains visible from the front side 41 can becovered with a bezel (not shown). The bezel may be formed, for example,from a stand-alone bezel structure that is mounted to the cover layer(not shown) formed over the OLED 31. The non-display area 211 remainingvisible from the front side 41 may also be hidden under an opaquemasking layer, such as black ink (e.g., a polymer filled with carbonblack) or a layer of opaque metal. Such an opaque masking layer may beprovided on a portion of the layers included in the flexible display.

In some embodiments, the semiconductor device 100 is coupled to aconductor 23 (e.g., in the form of pads or bumps) disposed in thenon-display area 211 using chip-on-film (COF), chip-on-plastic (COP) orany other suitable technologies. As will be described in further detailbelow, the non-display area 211 with the conductor 23 can be bent awayfrom the display area 212 so that the semiconductor device 100 ispositioned at the rear side 42 of the flexible display to reduce thesize of the non-display area 211 to be hidden by a bezel.

In some embodiments, the non-display area 211 may further includevarious additional components for generating a variety of signals orotherwise operating the OLED in the display area 212. In someembodiments, an inverter circuit, a multiplexer, an electrostaticdischarge (ESD) circuit, or the like may be placed in the non-displayarea 211 of the flexible display. In some embodiments, the non-displayarea 211 may further include components associated with functions otherthan operating the OLED of the flexible display. In some embodiments,the flexible display may include components for providing atouch-sensing function, a user-authentication function (e.g., afingerprint scan), a multi-level pressure-sensing function, atactile-feedback function, and/or various other functions for theelectronic device employing the flexible display. These components canbe placed in the non-display area 211 or provided on a separate printedcircuit that is connected to a connection interface of the flexibledisplay.

In some embodiments, parts of the flexible display may be defined by acentral flat portion 213 and at least one bend portion 214. In referenceto a bend line BL, the part of the flexible display 100 that remainssubstantially flat is referred to as the central flat portion 213,whereas the other part of the flexible display on the other side of thebend line BL is referred to as the bend portion 214. It should be notedthat the central flat portion 213 of the flexible display need not beperfectly flat. While the central flat portion 213 of the flexibledisplay is relatively more flat than the bend portion 214, the centralflat portion 213 can be curved in or curved out as depicted in FIG. 6.FIG. 6 is a schematic view illustrating a flexible substrate 21 of theflexible display according to aspects of the present disclosure in someembodiments. Referring to FIGS. 4, 5 and 6, in some embodiments, one ormore bend portions 214 exist next to the convex or concave central flatportion 213, and bend inwardly or outwardly along the bend line.

In some embodiments, the flexible display may be defined by a pluralityof bend lines BL. In some embodiments, multiple parts of the flexibledisplay can be bent along the bend lines BL. The bend line BL in theflexible display may extend horizontally (e.g., X-axis shown in FIG. 4),vertically (e.g., Y-axis shown in FIG. 4) or even diagonally. In someembodiments, the flexible display can be bent in any combination ofhorizontal, vertical and diagonal directions based on the desired designof the flexible display. In some embodiments, one or more edges of theflexible display can be bent away from the plane of the central flatportion 213 along the bend line BL. Although the bend line BL isdepicted as being located near the edges of the flexible display, itshould be noted that the bend lines BL can extend across the centralflat portion 213 or extend diagonally at one or more corners of theflexible display.

In some embodiments, the central flat portion 213 of the flexibledisplay 100 may be substantially flat, and one or more bend portions 214may be bent away along the bending line BL. The size of each bendportion 214 that is bent away from the central flat portion 213 need notbe the same. That is, the length of the flexible substrate 21 from thebend line BL to the outer edge of the flexible substrate 21 at each bendportion 214 can be different from other bend portions 214. Also, in someembodiments, the bend angle can vary between the bend portions 214.

As shown in FIG. 5, an organic light-emitting diode (OLED) 31 isdisposed on the flexible substrate 21, and an encapsulation layer (notshown) is further disposed on the organic light-emitting diode (OLED)31. In some embodiments, a part of the flexible substrate 21 is bent andpositioned at the underside of the display area 212 as depicted in FIG.5. In some embodiments, the semiconductor device 100 is placed at therear side 42 of the flexible display.

In some embodiments, the circuit 22 includes a plurality of conductivelines 221. The conductive lines 221 are configured to electricallyconnect between various components of the flexible display, such as thesemiconductor device 100 and the OLED 31. The circuit 22 fabricated inthe display area 212 and the non-display area 211 may transmit varioussignals via one or more conductive lines 221 to provide a number offunctions in the flexible display. In some embodiments, some conductivelines 221 may be used to provide connections between the circuit 22and/or other components in the central flat portion 213 and the bendportion 214 of the flexible display. Some of the conductive lines 221may be extended from the central flat portion 213 to the bend portion214. In such cases, some portions of the conductive lines 221 may beconfigured differently from the other portions to withstand the bendingstress. In particular, in some embodiments, some of the conductive lines221 laid over the bend portion 214 may include several features forreducing cracks and fractures of the conductive lines 221 to maintainproper interconnection.

In some embodiments, the conductive lines 221 include copper, aluminum,transparent conductive oxide, or other flexible conductors. In someembodiments, the conductive lines 221 of the flexible display may have amulti-layered structure, which may allow more flexibility with lesschance of breakage. In some embodiments, each conductive line 221 iselectrically connected to a conductor 23.

In the present disclosure, a method of manufacturing a flexible displayis disclosed. In some embodiments, a semiconductor device ismanufactured by the method. In some embodiments, a flexible display ismanufactured by the method. The method includes a number of operationsand the description and illustration are not deemed as a limitation ofthe sequence of the operations. FIG. 7 is a flowchart depicting anembodiment of the method of manufacturing the semiconductor device. Themethod includes operations 71, 72, 73 and 74.

FIGS. 8 to 17 are cross-sectional views and top schematic viewsillustrating exemplary operations for manufacturing a semiconductordevice and a flexible display of the present disclosure. In someembodiments, the operations of FIGS. 8 to 15 may be used to provide ormanufacture the semiconductor device similar to the semiconductor deviceillustrated in FIG. 2. In some embodiments, the operations of FIGS. 8 to17 may be used to provide or manufacture the flexible display similar tothe semiconductor device illustrated in FIG. 4.

The methods begin with operation 71, in which a substrate 11 includingsemiconductive material is provided. In some embodiments, in operation71, a base layer 15 is provided as shown in FIG. 8, and the base layer15 may be patterned using photolithography techniques.

In some embodiments, an ILD layer 14 is formed over the base layer 15extending along the first direction X. In some embodiments, an ILDsublayer 141 is formed over the base layer 15 extending along the firstdirection X as shown in FIG. 9. In some embodiments, the ILD layer 14can be formed by a deposition process, such as a CVD process.

In operation 72, a conductive pad 12 is formed on the substrate 11. Insome embodiments, a plurality of recesses 127 are formed in the ILDsublayer 141 as shown in FIG. 10. Each recess 127 penetrates the ILDsublayer 141. The recess 127 may be formed by removing portions of thetop dielectric sublayer 141 to expose at least a portion of theunderlying base layer 15.

In some embodiments, a photoresist material (not shown) is formed overthe ILD sublayer 141. The photoresist material is subsequentlyirradiated (exposed) and developed to remove a portion of thephotoresist material. Next, the exposed portions of the ILD sublayer 141are removed using, for example, a suitable etching process to form therecesses 127.

As shown in FIG. 11, recesses 127 are filled with a conductive material,thereby forming a metal interconnect layer 128 extending along the firstdirection X as shown in FIG. 11. The metal interconnect layer 128 may beformed using an electro-chemical plating process, an electroless platingprocess, PVD, ALD, the like, or a combination thereof.

Further in operation 72, in some embodiments, the conductive features120 are formed as shown in FIG. 12. The conductive feature 120 may beformed by first depositing a photoresist (not shown) on the metalinterconnect layer 128. The photoresist may then be patterned to coverportions where the conductive features 120 are desired to be located.Once the photoresist has been formed and patterned, portions of themetal interconnect layer 128 not covered by the photoresist can beremoved by a suitable etching process. Subsequently, after the removalof the photoresist, excess materials of the metal interconnect layer 128can be removed by a CMP or the like.

In some embodiments, additional ILD sublayers 141 are formed on the ILDsublayer 141 extending along the first direction X, wherein theadditional ILD sublayers surround the conductive features 120 as shownin FIG. 13.

Further in operation 72, in some embodiments, a passivation layer 13 isformed over the ILD sublayer 141 and the conductive features 120,wherein the passivation layer 14 extends along the first direction X, asshown in FIG. 14.

In some embodiments, recesses 131 are formed in the passivation layer 13as shown in FIG. 15. Each recess 131 penetrates the passivation layer13. The recesses 131 may be formed by removing portions of thepassivation layer 13 to expose at least a portion of the underlyingconductive features 120. Each recess 131 is free of right angle, so thatthe exposed portion of the conductive features 120 is free of rightangle from a top view perspective. Each exposed portion of theconductive features 120 is a conductive pad 12. In some embodiments, asemiconductor device 100 is thus formed.

In some embodiments, a photoresist material (not shown) is formed overthe top of the passivation layer 13. The photoresist material issubsequently irradiated (exposed) and developed to remove a portion ofthe photoresist material. Next, the exposed portions of the passivationlayer 13 are removed using, for example, a suitable etching process toform the recesses 131.

In operation 73, a flexible substrate 21 is provided. As shown in FIG.16, the flexible substrate 21 includes a circuit 22. The flexiblesubstrate 21 further includes a non-display area 211. In someembodiments, an organic light-emitting diode (OLED) 31 is formed overthe flexible substrate 21. In some embodiments, the OLED 31 is locatedin a display area 212 of the flexible substrate 21. In some embodiments,the circuit 22 includes a plurality of conductive lines 221. In someembodiments, each conductive line 221 is electrically connected to aconductor 23.

In operation 74, the conductive pads 12 of the semiconductor device 100are bonded to the corresponding conductors 23 of the circuit 22. In someembodiments, as shown in FIG. 17, the semiconductor device 100 isattached to the flexible substrate 21. In some embodiments, thesemiconductor device 100 is attached to the flexible substrate 21 byapplying a predetermined pressure to the semiconductor device 100. Insome embodiments, the semiconductor device 100 is attached to anon-display area 211 of the flexible substrate 21. In some embodiments,the conductive pad 12 is located between the substrate 11 and theflexible substrate 21.

Accordingly, the present disclosure provides a semiconductor device forattaching to a flexible display, a flexible display, and a method ofmanufacturing a flexible display. The semiconductor device includes aconductive pad that is free of right angle from a top view perspective.Consequently, when the semiconductor device is bonded or attached to theflexible display, the semiconductor device is not susceptible tocracking.

In some embodiments, a semiconductor device for attaching to a flexibledisplay is provided. The semiconductor device includes a substrateincluding semiconductive material, and a conductive pad disposed on thesubstrate. Each corner of the conductive pad is free of right angle.

In some embodiments, a flexible display is provided. The flexibledisplay includes a flexible substrate including a circuit, and asemiconductor device attached to the flexible substrate. Thesemiconductor device includes a substrate including semiconductivematerial, and a conductive pad disposed on the substrate. Each corner ofthe conductive pad is free of right angle.

In some embodiments, a method of manufacturing a flexible display isprovided. The method of manufacturing a flexible display includesproviding a substrate including semiconductive material, and forming aconductive pad on the substrate, wherein each corner of the conductivepad is free of right angle. The method further includes providing aflexible substrate, and bonding the conductive pad to a conductor of acircuit of the flexible substrate.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A semiconductor device for attaching to aflexible display, comprising: a substrate including semiconductivematerial, a first pad density area, and a second pad density area havinga higher pad density than the first pad density area; and a plurality ofconductive pads disposed on the substrate; wherein each corner of eachconductive pads is free of right angle, the substrate has a pair of longsides from a top view perspective, the shape of each of the conductivepads is a parallelogram, and each of the conductive pad has a pair oflong sides and a pair of short sides from a top view perspective, aportion of the conductive pads have the long sides sloped away from thefirst pad density area and toward one long side of the substrate, andthe rest of the conductive pads have the long sides sloped toward thefirst pad density area and toward the other long side of the substrate.2. The semiconductor device of claim 1, wherein the shape of theconductive pad is a multi-layered conductive pad.
 3. The semiconductordevice of claim 1, wherein the conductive pad is arc-shaped from a topview perspective.
 4. The semiconductor device of claim 1, wherein thesubstrate further includes a passivation layer surrounding theconductive pad.
 5. The semiconductor device of claim 4, wherein thepassivation layer includes silicon nitride (SiN), silicon carbide (SiC),silicon oxide (SiO), and/or silicon oxynitride (SiON).
 6. Thesemiconductor device of claim 1, wherein the semiconductive materialincludes silicon, silicon-germanium, or other semiconductor materialsincluding III-V or II-VI materials.
 7. The semiconductor device of claim1, wherein the short sides of each of the conductive pads are parallelto the long sides of the substrate.
 8. The semiconductor device of claim1, wherein the low pad density area is located between the high paddensity areas.
 9. The semiconductor device of claim 1, wherein the lowpad density area is located at the center of the substrate.
 10. Aflexible display, comprising: a flexible substrate including a circuit,and a semiconductor device attached to the flexible substrate; whereinthe semiconductor device comprises: an interlayer dielectric layerincluding a first pad density area, and a second pad density area havinga higher pad density than the first pad density area from a top viewperspective; and a plurality of conductive pads surrounded by theinterlayer dielectric layer and bonded to a conductor of the circuit,wherein each corner of the conductive pad is free of right angle, theinterlayer dielectric layer has a pair of long sides from a top viewperspective, the shape of each of the conductive pads is aparallelogram, and each of the conductive pad has a pair of long sidesand a pair of short sides from a top view perspective, a portion of theconductive pads have the long sides sloped away from the first paddensity area and toward one long side of the interlayer dielectriclayer, and the rest of the conductive pads have the long sides slopedtoward the first pad density area and toward the other long side of theinterlayer dielectric layer.
 11. The flexible display of claim 10,wherein the shape of the conductive pad is a parallelogram or trapezoidfrom a top view perspective.
 12. The flexible display of claim 10,wherein the conductive pad is arc-shaped from a top view perspective.13. The flexible display of claim 10, wherein the flexible substrateincludes polyimide.
 14. The flexible display of claim 10, wherein thesemiconductor device is attached to a non-display area of the flexiblesubstrate.
 15. The flexible display of claim 10, wherein the conductoris located at a non-display area of the flexible substrate.
 16. Theflexible display of claim 10, further including an organiclight-emitting diode (OLED) formed over the flexible substrate.
 17. Theflexible display of claim 16, wherein the organic light-emitting diode(OLED) is located at a display area of the flexible substrate.
 18. Theflexible display of claim 16, wherein the organic light-emitting diode(OLED) is located at a central flat portion of the flexible substrate.19. The flexible display of claim 10, wherein the semiconductor deviceis positioned at the rear side of the flexible display.
 20. Asemiconductor device for attaching to a flexible display, comprising: asubstrate including a base layer, an interlayer dielectric layer formedon the base layer, and a pre-metal dielectric layer formed between thebase layer and the interlayer dielectric layer; wherein the interlayerdielectric layer includes a first pad density area and a second paddensity area having a higher pad density than the first pad density areafrom a top view perspective; a plurality of conductive pads disposed onthe second pad density area; wherein each corner of the conductive padsis free of right angle, the shape of each of the conductive pads is aparallelogram from a top view perspective, part of the conductive pad isslanted away from the first pad density area, and the other part of theconductive pad is slanted toward the first pad density area.